1. Field of the Invention
The present invention relates to an aromatic polycarbonate resin composition. More particularly, the present invention is concerned with an aromatic polycarbonate resin composition comprising (A) an aromatic polycarbonate or a resin mixture of an aromatic polycarbonate and at least one organic polymer resin other than an aromatic polycarbonate, and (B) at least one aromatic group-containing silicone compound selected from the group consisting of an aromatic group-containing silicone compound having a linear configuration and an aromatic group-containing silicone compound having a cyclic configuration, wherein the component (B) contains an aromatic group in a specific amount. The aromatic polycarbonate resin composition of the present invention has not only excellent flame retardancy, but also excellent melt fluidity and excellent melt-molding stability (i.e., substantially no variation or only small variation in the quality of shaped articles obtained by melt-molding). By molding the aromatic polycarbonate resin composition of the present invention, there can be obtained shaped articles having excellent mechanical properties, excellent light stability and excellent appearance.
2. Prior Art
Polycarbonates, which are light in weight and have excellent impact resistance, have been used in various fields, such as automobile parts, parts for use in household electric appliances and parts for use in office automation machines. However, polycarbonates are easily flammable, and the use of polycarbonates is limited due to their flammability.
As a method for imparting flame retardancy to resins, it is known to add thereto flame retardants, such as halogen-containing flame retardants, phosphorus-containing flame retardants and inorganic flame retardants. The objective of imparting flame retardancy to resins has been attained to some extent by the use of such flame retardants. However, the demand for improved safety in the accident of fire has increased in recent years. In accordance with the increasing demand, studies for developing improved techniques for imparting flame retardancy to resins have been made in the art. In addition, it has also been desired for these flame retardancy-imparting techniques to have advantages in that no environmental problem is posed or no lowering of the mechanical properties of resins is caused.
Techniques are also known of using organic silicon compounds as flame retardants for resins. For example, Unexamined Japanese Patent Application Laid-Open Specification No. 63-41565 discloses a smoke suppressant comprising a hydrocarbon, a silicone and zinc borate. U.S. Pat. Nos. 4,497,925 and 4,387,176 each discloses a flame retardant resin composition containing a di-methylsilicone. Each of the silicones described in the above-mentioned three prior art documents has an extremely small content of an aromatic group (less than 5 mole %). When such a flame retardant (containing a silicone having a low aromatic group content) is mixed with an aromatic group-containing resin to obtain a resin composition, a phase separation is likely to occur between the silicone and the resin due to a poor compatibility therebetween. As a result, when such a resin composition is molded to form a shaped article, a problem arises in that the mechanical properties of the shaped article, such as impact strength, are lowered. Therefore, these types of flame retardants are unsatisfactory for practical use.
Unexamined Japanese Patent Application Laid-Open Specification No. 63-162756 discloses a resin composition comprising an aromatic polycarbonate, a polyolefin and a silicone fluid, wherein the resin composition is described as exhibiting an improved abrasion resistance. However, the silicone described in this prior art document has a very low aromatic group content. Therefore, the resin composition disclosed in this prior art document has substantially the same problem as described above in connection with the above-mentioned Unexamined Japanese Patent Application Laid-Open Specification No. 63-41565 and U.S. Pat. Nos. 4,497,925 and 4,387,176.
Unexamined Japanese Patent Application Laid-Open Specification Nos. 10-139964 and 11-140294 each disclose a flame retardant aromatic polycarbonate resin composition containing a branched methylphenylsilicone and/or a crosslinked methylphenylsilicone. However, due to the branched and crosslinked structures thereof, the above-mentioned methylphenylsilicones exhibit poor compatibility with an aromatic polycarbonate resin. As a result, each of these branched and crosslinked methylphenylsilicones has a problem in that the dispersibility thereof in the resin composition is poor. Further, the aromatic polycarbonate resin composition disclosed in this prior art document has a problem in that the flame retardancy thereof is poor.
A methylphenylsilicone having no branched or crosslinked structure is known and used as an oil for a diffusion pump or a high temperature oil bath. However, with respect to this type of methylphenylsilicone, there has been no report suggesting that a polycarbonate resin composition having not only an excellent flame retardancy but also excellent mechanical properties has been obtained by the combined use of the above-mentioned silicone and an aromatic polycarbonate.
Further, as a combination of a silicone and a resin in other than a polycarbonate, a composition comprising a polyphenylene ether and a phenylsiloxane is known (see Unexamined Japanese Patent Application Laid-Open Specification No. 5-70680). In this composition, an aromatic group-containing polyorganosiloxane having a linear configuration is used as a flame retardant. However, since this composition employs a polyphenylene ether as a resin component, this composition has poor impact strength and poor light resistance. Therefore, this prior art technique gives no solution for the problems accompanying polycarbonate resins.
In this situation, the present inventor has made extensive and intensive studies with a view toward developing a polycarbonate resin composition which is free from the above-mentioned problems, specifically, a polycarbonate resin composition which is advantageous not only in that it has excellent flame retardancy, excellent melt fluidity and excellent melt-molding stability (i.e., substantially no variation or only small variation in the quality of shaped articles obtained by melt-molding), but also in that it can be used for producing a shaped article having excellent mechanical properties, excellent light stability and excellent appearance. As a result, it has unexpectedly been found that, by using at least one specific, aromatic group-containing silicone compound selected from the group consisting of an aromatic group-containing silicone compound having a linear configuration and an aromatic group-containing silicone compound having a cyclic configuration, wherein the silicone compound contains an aromatic group in a specific amount, not only can a great flame retardancy be imparted to an aromatic polycarbonate, but also the above-mentioned other properties of an aromatic polycarbonate can be improved. The present invention has been completed, based on this novel finding.
Accordingly, it is a primary object of the present invention to provide an aromatic polycarbonate resin composition which is advantageous not only in that it has excellent flame retardancy, excellent melt fluidity and excellent melt-molding stability (i.e., substantially no variation or only small variation in the quality of shaped articles obtained by melt-molding), but also in that it can be used for producing a shaped article having excellent mechanical properties, excellent light stability and excellent appearance.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and claims.